Environmental Engineering Reference
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of azo dyes in anoxic condition was in
uenced by various substrates used in cell
growth medium. Although, azo dye decolorization under anoxic condition was non-
speci
c, limitation of this method was requirement of yeast extract or peptone. This
makes the process economically in viable for industrial-scale application unless
alternate cheaper sources are identi
ed (Nigam et al. 1996 ; Chen et al. 2003 ; Moosvi
et al. 2005 ).
5 Decolorization of Azo Dyes Under Aerobic Condition
5.1 Decolorization of Azo Dyes Under Static Condition
The optimum pH for decolorization of azo dyesat static condition is 7.0
8.0. The
pure bacterial cultures isolated from textile dye contaminated soil, such as Pseu-
domonas sp. SUK 1, Kocuria rosea, Rhizobium radiobacter, Bacillus sp.VUS,
Commamonas sp. UVS,Exiguobacterium sp. RD3, Proteus sp. SUK 7; Bacillus sp.
ADR; and Pseudomonas sp. SU-EBT were ef
-
ciently decolorized azo dyes at static
condition than shaking condition (Kalme et al. 2007 ; Parshetti et al. 2007 ; Dawkar
et al. 2008 ; Dhanve et al. 2008a , b ; Jadhav et al. 2008 ; Kalyani et al. 2008 ; Patil
et al. 2008 ; Telke et al. 2008 , 2009 ). The pure bacterial cultures of Pseudomonas
sp. SUK1 and Rhizobium radiobacter MTCC 8161 were able to tolerate and
degrade the higher concentration (more than 1 g l 1 ) of azo dyes (Kalyani et al.
2008 ; Telke et al. 2008 ). The recent reports showed that the combination of yeast
extract with urea and agricultural wastes (bagasse powder, wheat bran, rice bran and
wood shaving) were effective medium for the decolorization of azo dyes (Jadhav
et al. 2008 ; Telke et al. 2008 ) at static condition.
5.2 Decolorization of Azo Dyes Under Shaking Condition
For a long time it was thought that azo dyes were recalcitrant under aerobic con-
ditions. A bacterial strain S5, derived from Hydrogenophaga palleronii S1, min-
eralized sulfonated azo dyes by utilizing them as carbon and nitrogen source for cell
growth (Blumel et al. 1998 ). The recent studies have shown that the pure bacterial
culture (Unidenti
ed KMK 4, strain S5, E. coli NO 3 and Flavobacterium sp.
ATCC39723) and mixed bacterial culture (unidenti
ed BF1, BF2 and Pseudomo-
nas putida MTCC 1194) have ability to degrade higher concentration (1 g 1 )of
azo dyes (Cao et al. 1993 ; Chang and Kuo 2000 ; Senan and Abraham 2004 ; Kodam
et al. 2005 ). Aerobic bacterial cultures were reduced the azo linkage by the
involvement of azo reductases and oxidases or combination of both enzymes. Azo
reductases isolated from aerobic bacteria have a narrow substrate range (Kulla
1981 ; Zimmermann et al. 1982 , 1984 ; Kulla et al. 1983 ). The involvement of
peroxidase was reported in azo dye oxidation by Cao et al. ( 1993 ).
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